Is their a tension pulley on it, If so the spring on the pulley could need replaced, Also if there is a cover on the mowing deck take that off and check that belt.

on hours the hole that holds the blade were worn out and they would spin but the minute it hit the grass it would just stop.

Melinda, there are any number of knowledgeable folks on the forum who can help out, but they're going to need a little more information. A good start would be to copy the mower's model number from a tag that is under the seat; just tip the seat forward and look for the tag, then report that model number back here.

The solution might very well be a simple one. My guess is that whoever put the new belts on routed them on the wrong side of the tension idler. The idler is what tightens up the belt when the mower blades are engaged, and it pushes against the OUTSIDE of the belt; at a glance, it appears that the idler should be inside the belt, when it actually needs to be outside.

Please post the mower model number.

Could be it the electric PTO clutch that drives the blades needs to be adjusted.

You should find the information on how to do this in your owners manual or on the web.

I will not go into details on how to preform the work for I have no clue as to which or type or brand of Electric PTO your mower has. I do not want to tell you how to adjust and check one type and give you the wrong information for your mower.

When it comes to this type of repair. Always start with the simplest thing and work your way from there.

The adjustment on an "adjustable PTO clutch" is only to initiate engagement. It is called air gap adjustment.
Adjustment on those types clutches is necessary after many hours of run time accumulation has resulted in enough wear of the friction surfaces to increase the air gap when the clutch is not engaged. Eventually, the wear causes a wide enough air gap to be present that the electromagnetic coil in the clutch is unable to "reach out" and grab the driven disc of the clutch to draw it into engagement.
Adjusting that air gap only makes it easier for the clutch to engage, it DOES NOT make the clutch lock into a tighter engagement.
If, the blade belts are seen to be spinning at all, the clutch is engaging, and cannot be made to engage any more.
The fact that the belt was replaced makes it very likely that the belt is either mis-routed through the pulleys, or the tensioning pulley operating spring has been hooked into an anchor point where it should not be.
Often, there is a belt routing diagram decal affixed directly to the deck.
If no decal, refer to the owners manual for a belt routing diagram (and possible photos or drawings).
If you don't have the owners manual, go to the MTD website with your full, technical model number AND serial number and download your owners manual free.

Or the belt is a third party belt that isn't quite on specification or is just wrong for the application.