Can i use 3 12volt batteries in a golf cart instead of 6 6volt batteries

You question is very vague as to what type of push cart your needing wheels for.

Taking a guess your describing a 3-wheel GOLF push cart, this site sells replacement parts. (If not a golf cart, please post a new question describing the make and model of cart).

https://news.sunmountain.com/golf-push-pull-cart-parts/

https://www.golfcarcatalog.com/golf-cart-blog/golf-cart-battery-bank-wiring-in-series/
This should solve your problem.
Next time you want to take something apart, be sure to take a picture or 2, before you disconnect anything. That will help you put it back like it was.

If the battery is not maintenance free, check the water levels in each cell. If you need to add water be sure to use distilled. Never use tap water unless an absolute necessity to get the vehicle running as it will destroy the battery.
Make sure the charger is set to 12v. Some chargers will have a 6v setting that typically are used in golf carts, boats, off grid solar.
Check the terminals on the clamps for corrosion.
Be certain that the clamps are tight on the battery posts.
If everything checks out, get a new charger.

Basic EZGO Golf Cart Problems And How To Fix -

www.golfcarthotrod.com > Golf Cart Repair
Apr 30, 2010 - Electric E-Z-Go Golf Carts are becoming more popular every day ..... I have a ezgo carryall gas golfcart. it has began to pour smoke from rear.

DONT KNOW

golf cart ? sorry do not play golf as its a snobs game so i know nothing about golf carts

http://www.buggiesgonewild.com/electric-ezgo/1536-basic-ezgo-electric-golf-cart-wiring-manuals.html

What I did was to buy a good blue tooth speaker and connect to my cell phone. 3 hrs on the golf course and 10% of the cell battery

Sams club $77 each

I have a 96 EZ GO gas golf cart with loose steering. What parts are normally needed to correct this problem and are special tools required for me to replace the parts.
Thanks,
Bob