Should have a 3/4 inch Tapered shaft. Wheel May or May not have a Key Lock or snap ring , or pin holding it in place. Inspect to see if any of these apply. Loosen the center Nut until its outedge is even with the end of the threaded shaft. Wedge your knees behind and under the wheel to apply pressure and use a rubber hammer or regular hammer and block of wood to forcefully hit the shaft. You have to break the tapered shaft "Wedge" effect to get the wheel free. It takes some pounding and some pulling but you can and will get it free. Heating the shaft might help too.
Good Luck.