5d with unknown Firmware to new 5D3

I have read a few topics on this but want to raise this in an updated post. I have a 5 that quit working overnight. I bought a 5d3 and want to move the diskpack over. I do not know what the old one had for Firmware but it wasn’t original. Probably 2 firmware versions old. I know the 5 can be moved to the 5d3 but with different firmware will this be a problem?

Thank you for any advice.