That pump can only build 51 PSI total. With 15’ lift and a little friction loss, I figure 42 PSI max is all you can get. If your gauge is a couple pounds off, as most gauges are, 38 PSI doesn’t surprise me. A jet pump would have made much better pressure.
However, you should be able to loosen on the large adjustment screw in the pressure switch so it will shut off at 38 PSI. Of course that means you only have 18 PSI before the pump starts. I wouldn’t be happy with that. I would take the pump back to whoever told you it would work. Those pumps are made to produce 40 to 50 GPM at 20 to 30 PSI, but they were not meant to deliver much (enough) pressure.
If you can’t get a jet, a submersible would be even better.