Activate the new wifi setup of the 620. Maybe, you have to use the new kybd., etc., but once done and all seems to work, then install the old kybd., etc. and see if it works. Its not going to hurt your new PC, the worse is it won't work or you need to install the drivers, for a 100% install of old stuff have that handy. If not available, Dell support website for your old 530, should have what you need.
Old computer was an Inspiron 530 and came with wireless keyboard and mouse combo. Will my old combo work with my new Dell 620, which has a wireless card?