Replacing tires, mountain bike

I inherited a mountain bike from my son (Raleigh Teton 1986) and I would
like to

be able to use it just for exercising in the street (concrete, asphalt and
occasionally

gravel) and I need to replace the worn tires. The ones that I found seem to
have rough

treading for rough terrain but I would prefer tires that give me a smooth
ride.

Could I replace the originals with a set of tires that are a bit smother?

By the way, the tire are 26 x 2.125

Any suggestion where could I get them? Online or I am in South Florida.



Thank you in advance



Kathy