Hi, I am currently using an Intel I3-2120 and I am looking at upgrading to an I5-9400F processor, do you know if the motherboard and RAM will be compatible or if I will need to upgrade it, thanks
You must contact the motherboard manufacturer and ask them what processors are supported by your board's bios. Then, you can select from those processors.
It is extremely unlikely that you can do the upgrade you want. You are talking about SEVEN YEARS difference.