We need to know the thread unfortunately as there were a variety of freewheel threads and unless it is Shimano compat. I'd tend to shy away. If you have a Shimano freewheel that can be screwed onto the wheels I'd take them.
If they're from the MTB range (guessing they are) then you'll be fine as any Aris/sachs/shimano freewheel will fit them. Had a variety of these and bullseyes and they all worked with all standard freewheels out there. It's only when you go back in time further that the problems start, 5 and 6 speed freewheels had a variety of fittings but as this is a 135mm I'd assume it's a modern fit.