I did a similar thing for an old Diamondback MTB, at least what they called a MTB 20+ years ago, for my daughter to tool around on. 26x1.5 road tires from the LBS, can't tell you the brand, it was the only pair they had at the time. Definitely made for a much smother ride to get rid of the knobby tires and she is more inclined to ride it around now than before.

******* Edit

Got home and looked, they are Kenda Kwest, 65 psi max., they appear fine ( it's not a bike I ride ). I did notice though ...
The ---> Drive Direction marking on the side wall of the rear tire was pointed the wrong way. WTF, stupid tire.