I have been using a 20' extension cord I made with 10 gage copper with the black rubber insulation for years for my belt grinder and 2 hp table saw.
I have a 20 foot extension cord I use for my 50 amp welder. It is made of 6 gage copper wire.
I would ask an electrician what wire size you would need for 75 feet, but if you don't mind spending the money, it should work fine.
If it is a three prong plug, the third prong is a ground wire.
the main consideration is how you plan to run it. If it is on the ground, there is a big safety consideration. If you pla