Need help after hardware upgrade on Windows 10

So I just tonight upgraded some of my hardware in my old rig. I was running an msi b450 gaming plus max and a ryzen 7 3600x.

Tonight I swapped it out with a new msi b550 tomahawk max wifi (got it on marketplace for $140 Cad) and a new ryzen 7 5800xt.

Everything is hooked up, it powers on, but I get a BOOTMGR IS MISSING, PRESS CTRL ALT DEL.

Everything is hooked up, I thought I had my drives hooked up in order? I went into the bios and adjusted the boot to go off of what I think is my main drive. Still an issue.

I'm still using windows 10, booting in LEGACY, NOT UEFI, my c drive is still mbr.

It was working without issue before I did the upgrade.