Question Where is the 3pin 5v adreassable header Asus x570 wifi plus i am using a cooler master h500p mesh and it comes with a fan splitter preinstalled

According to the manual and specifications, it does not have one. It seems to ONLY have four pin headers. An Aura 4 pin RGB header and a Gen 2 4 pin addressable header. No 3 pin addressable header. If you need one, you may need to purchase a third party controller.
 
Specifications and the board diagram don't show that though. I think that part of the manual is copy pasted from another manual or a misprint. Either that, or the rest of the manual is wrong. Based on these, taken directly from the manual for that board on the ASUS website, there are ZERO three pin RGB headers on that board.

2 x Aura RGB Strip Header(s)
1 x Addressable Gen 2 header(s)
2 x USB 2.0 connector(s) support(s) additional 4 USB 2.0 port(s)
1 x M.2 Socket 3 with M Key, type 2242/2260/2280/22110 storage devices support (SATA mode & X4 PCIE mode)
1 x M.2 Socket 3 with M Key, type 2242/2260/2280/22110 storage devices support (SATA mode & X4 PCIE mode)
1 x SPI TPM header
8 x SATA 6Gb/s connector(s)
1 x CPU Fan connector(s)
1 x CPU OPT Fan connector(s)
3 x Chassis Fan connector(s)
1 x AIO_PUMP connector
1 x 24-pin EATX Power connector(s)
1 x 8-pin ATX 12V Power connector(s)
1 x 4-pin ATX 12V Power connector(s)
1 x Front panel audio connector(s) (AAFP)
1 x System panel(s)
1 x Clear CMOS jumper(s)
1 x COM port header
1 x USB 3.2 Gen 1 (up to 5Gbps) connector support additional 2 USB ports


71HpfmX.png



ASUS TUF GAMING X570-PLUS (WI-FI)1-3Chapter 1
Layout contents
Connectors/Jumpers/Buttons and switches/Slots Page
1. ATX power connectors (24-pin EATXPWR; 8-pin EATX12V_1; 4-pin EATX
12V_2) 1-15
2. CPU, CPU optional, and chassis fan connectors; AIO pump connector (4-pin
CPU_FAN, 4-pin CPU_OPT, 4-pin CHA_FAN1-3; 4-pin AIO_PUMP) 1-14
  1. SPI_TPM connector (14-1 pin SPI_TPM) 1-10
  2. AM4 CPU socket 1-4
  3. AURA RGB headers (4-pin RGB_HEADER1/2) 1-17
  4. DDR4 DIMM slots 1-4
  5. Q LEDs 1-8
8. Addressable Gen 2 header (4-pin ADD_GEN2) 1-18
  1. USB 3.2 Gen 1 connector (20-1 pin U32G1_12) 1-12
  2. M.2 Socket 3 1-16
  3. AMD Serial ATA 6 Gb/s connectors (7-pin SATA6G_1-8) 1-11
  4. Clear RTC RAM jumper (2-pin CLRTC) 1-9
  5. System panel connectors (20-5 pin PANEL) 1-13
  6. USB 2.0 connectors (10-1 pin USB78, USB910) 1-12
  7. Serial port connector (10-1 pin COM) 1-15
  8. Front panel audio connector (10-1 pin AAFP) 1-10
 
Specifications and the board diagram don't show that though. I think that part of the manual is copy pasted from another manual or a misprint. Either that, or the rest of the manual is wrong. Based on these, taken directly from the manual for that board on the ASUS website, there are ZERO three pin RGB headers on that board.

2 x Aura RGB Strip Header(s)
1 x Addressable Gen 2 header(s)
2 x USB 2.0 connector(s) support(s) additional 4 USB 2.0 port(s)
1 x M.2 Socket 3 with M Key, type 2242/2260/2280/22110 storage devices support (SATA mode & X4 PCIE mode)
1 x M.2 Socket 3 with M Key, type 2242/2260/2280/22110 storage devices support (SATA mode & X4 PCIE mode)
1 x SPI TPM header
8 x SATA 6Gb/s connector(s)
1 x CPU Fan connector(s)
1 x CPU OPT Fan connector(s)
3 x Chassis Fan connector(s)
1 x AIO_PUMP connector
1 x 24-pin EATX Power connector(s)
1 x 8-pin ATX 12V Power connector(s)
1 x 4-pin ATX 12V Power connector(s)
1 x Front panel audio connector(s) (AAFP)
1 x System panel(s)
1 x Clear CMOS jumper(s)
1 x COM port header
1 x USB 3.2 Gen 1 (up to 5Gbps) connector support additional 2 USB ports


71HpfmX.png



ASUS TUF GAMING X570-PLUS (WI-FI)1-3Chapter 1
Layout contents
Connectors/Jumpers/Buttons and switches/Slots Page
1. ATX power connectors (24-pin EATXPWR; 8-pin EATX12V_1; 4-pin EATX
12V_2) 1-15
2. CPU, CPU optional, and chassis fan connectors; AIO pump connector (4-pin
CPU_FAN, 4-pin CPU_OPT, 4-pin CHA_FAN1-3; 4-pin AIO_PUMP) 1-14
  1. SPI_TPM connector (14-1 pin SPI_TPM) 1-10
  2. AM4 CPU socket 1-4
  3. AURA RGB headers (4-pin RGB_HEADER1/2) 1-17
  4. DDR4 DIMM slots 1-4
  5. Q LEDs 1-8
8. Addressable Gen 2 header (4-pin ADD_GEN2) 1-18
  1. USB 3.2 Gen 1 connector (20-1 pin U32G1_12) 1-12
  2. M.2 Socket 3 1-16
  3. AMD Serial ATA 6 Gb/s connectors (7-pin SATA6G_1-8) 1-11
  4. Clear RTC RAM jumper (2-pin CLRTC) 1-9
  5. System panel connectors (20-5 pin PANEL) 1-13
  6. USB 2.0 connectors (10-1 pin USB78, USB910) 1-12
  7. Serial port connector (10-1 pin COM) 1-15
  8. Front panel audio connector (10-1 pin AAFP) 1-10
It's right there
Addressable Gen 2 header (4-pin ADD_GEN2)
It's inline 4 pin with one pin missing.
 
They don't say four pin if it's a three pin. Ever. And on motherboard diagrams it always shows the missing pin as just a white square, not an actual pin like the other three pins. I could show you hundreds of boards like that. I'm not saying this isn't a mistake by ASUS, but if it IS, it's an enormous one. It's a very good way to completely fry some hardware by plugging into the wrong type of RGB header.