Excellent upgrade!! 😃 That’s wonderful you got the new CPU, you will notice a differencein spped in everything immediately!
Take out the 5700x3D, put 2600 back in and repaste heatsink. Turn on computer flash BIOS to the last version available for B450 Carbon AC. Read BIOS revisions notes to see if any say do not skip ahead until flashing this version of BIOS because if say version 103 says do not jump to lastest before updating to this version but you only flash version 110, there will be a problem with motherboard because info in BIOS is missing so board can’t boot normally.
But if you flash version 103, wait for it to finish, reboot, flash version 110, wait for it to finish, reboot, wait for desktop, then you should be 100% good for board to boot 5700x3D. Those version numbers are made up examples, don’t go looking for those BIOS version numbers on the MSI page
Use Win 11 LTSC, unplug ethernet, select do not have internet, it will ask you to create a local account