As always, go to the manufacturer spec page.
This one?
https://www.msi.com/Motherboard/B450M-GAMING-PLUS/Specification
"Supports PCIe 3.0 x4 (1st, 2nd and 3rd Gen AMD Ryzen™/ Ryzen™ with Radeon™ Vega Graphics and 2nd Gen AMD Ryzen™ with Radeon™ Graphics) or PCIe 3.0 x2 (Athlon™ with Radeon™ Vega Graphics) and SATA 6Gb/s 2242/ 2260 /2280/ 22110 storage devices "
Assuming you have the correct CPU, the Samsung 980 will work.
Be sure you're not referring to the 980
Pro. (PCIe 4.0)
RAM?
"2 x DDR4 memory slots, support up to 64GB *ComboPI 1.0.0.3-based and above BIOS are required.
Supports 1866/ 2133/ 2400/ 2667Mhz (by JEDEC)
Supports 2667/ 2800/ 2933/ 3000/ 3066/ 3200/ 3466 MHz (by A-XMP OC MODE)"