The rd on the left is a .38 S&W SPL +P.
The rd on the right is a .38 S&W.
Yours is the one left. Some .38 SPL guns will chamber a .38 S&W rd but the rds are different and have different dimensions. Don't interchange them.
You do not have to shoot +P rds in it but you need to get ammo that is labled either .38 S&W SPL or .38 SPL. Same rd, just labeled differently, depends who makes it. +P rd will be a hotter loaded rd. As long as you are just shooting at paper and unless you are loading for defense then there's no need to spend the extra money for +P and beat your gun with the hotter rd.
I can't think of any company who is making .38 S&W guns right now. Lots of older guns chambered for that rd. Hasn't been much modern development of that rd and the companies that load that rd tend to keep them pretty mild due to all the old, and often cheap, guns chambered for it.