Upgrading my motherboard and CPU - Moving over old HDD and SSD

[simo375i]

I would like to upgrade my motherboard and CPU but i quite simply cannot find a simple explanation of how to go about it. My current MB is a MSI B150M Night Elf and my CPU is an I5-6400. Now what i want to replace those two with is a MSI Z370 Gaming M5 motherboard and an I5-8400.
What i need to know is: Can i plug in my old 1TB HDD and expect it to work no problem (This HDD doesn't hold my OS)
And how do i go about installing my 250GB SSD (This holds my OS) without losing all the files (Pictures, videos and etc.) on it if i have to reinstall Windows?

I have never installed Windows before so i'm kinda new to this segment of fiddling with computers. Also if this is posted in the wrong category please do let me know where it should be otherwise posted so i can correct my mistake.

-Simon

 

[Hellfire13]

First, backup all your important(pics/vids/etc) files from the SSD to HDD or some other media.
Second, when the rest of the 8400 setup is complete, attach the SSD only to install the OS.
Before installing the OS, the installation will give you the option to format the drive. Format it and follow the prompts to install the OS. Not too difficult.
Once the OS is installed and the pc is up and running, shut it down and attach the HDD.
Switch on the pc and enter 'boot device priority" in BIOS to sequence the SSD as primary and the HDD as secondary.
Restart the pc and you should be all good.

 

[simo375i]

First, backup all your important(pics/vids/etc) files from the SSD to HDD or some other media.
Second, when the rest of the 8400 setup is complete, attach the SSD only to install the OS.
Before installing the OS, the installation will give you the option to format the drive. Format it and follow the prompts to install the OS. Not too difficult.
Once the OS is installed and the pc is up and running, shut it down and attach the HDD.
Switch on the pc and enter 'boot device priority" in BIOS to sequence the SSD as primary and the HDD as secondary.
Restart the pc and you should be all good.

Alright. Can i just use the old Windows disc and key to install the OS again afterwards?

 

[Hellfire13]

If its a retail disc, the key can be reused... https://answers.microsoft.com/en-us/windows/forum/windows_10-windows_install-winpc/windows-10-olp-vs-retail-vs-oeioem/73679bd3-3457-4511-8934-755ee65f180f?auth=1

 

[simo375i]

If its a retail disc, the key can be reused... https://answers.microsoft.com/en-us/windows/forum/windows_10-windows_install-winpc/windows-10-olp-vs-retail-vs-oeioem/73679bd3-3457-4511-8934-755ee65f180f?auth=1

I had my PC built by somebody and i got the disc with the PC and a little peice of paper with some notes like versions and codes. One of them says "Key type: Retail" so that should be it. Thanks for the help 😀