The Nissan Path

I noticed both of my ubolts are gone, one i knocked off after just wiggling it a little bit. These are the ubolts after the two cats where the join into a single tube. Should I put new ones on? Or are they probably rest welded together anyway? I guess I can try to see if there is a leak by spraying soapy water. If I should replace- anyone have part number?

You can pick up U-bolts for a few dollars each. They are sized according to the pipe size diameter, so you really don't need a part number. If it's before the main muffler, it's probably 2-inch and if it's after, likely 2-1/4"...but it'd be best to measure and be sure.