No, you cannot connect a 4-pin PSU connector to a B450M board.
No, you cannot connect a 4-pin PSU connector to a B450M board.
It should work without issues, but don’t count on overclocking the CPU. Use a PSU with an 8-pin connector; cheaper options are available for around $50 to $60.
Are you repurposing the PSU in another project? If so, consider a budget-friendly 500-600 watt unit—some are available for around fifty dollars. These custom PSUs may be prone to issues and not very efficient, but if you decide to keep using it, don’t anticipate overclocking your CPU.
I won't be upgrading right now and I'll handle the PSU upgrade later.