My home has provisions for a bathroom roughed into the cement basement floor. There is a toilet flange and two drain pipes, one for a sink and another for a shower. The drainpipe for the shower sticks up through the floor approximately three inches. The center of the drainpipe is 20 inches away from one wall and 21” away from the other wall (currently a cement block wall). Based on a conversation with my local Lowe's store, this drain does not match up with any showers. They said I would have to block the shower and plumb from the shower drain to the floor drain. Can anyone tell me how to do this? Thanks for your help.

'Based on a conversation with my local Lowe's store, this drain does not match up with any showers. They said I would have to block the shower and plumb from the shower drain to the floor drain.'

M-I-C K-E-Y MOUSE! That's the option Lowe's gave you? Platform the shower with a indirect waste? You were roughed in for a custom tile shower, Is there a shower dap out cut in the floor or is it level?
You install a PVC flange type shower drain,(see image) and plastic shower pan and frame and enclose the shower.
Your other option,( with the exception of platforming the base,) would be to purhase a base and move the trap and raiser to accommodate it. I can give you instructions on any one of the three options if you wish. I just wanted you to know that you have them. Which one will you choose? Regards, Tom