A shower drain moved to install a new shower can’t raise the floor to put in an elbow. The shower floor will have to be too high and connecting to the existing drain will be a nightmare. Moving the drain is not all that difficult once you accept some cement will have to be broken.
First get a 10 or 12# sledge hammer and beat an eight-inch spot near the existing drain until you can see dirt. Then take a small shovel or garden trowel and dig underneath the cement a little. Now hit the cement next to that area with the sledge and the concrete will break easily.
Once you have a hole large enough, about 12-inches in diameter, you can dig down to the bottom of the trap and locate the direction the drain is running.
Once you have contact with the lateral run of pipe you can check the size of the pipe, it should be about 2 3/8 inches outside diameter. That would be called two-inch pipe because pipe is measured on the interior, not the exterior.
No matter what size the pipe is, you can cut it and using a Fernco rubber coupling, convert it to PVC pipe and locate the drain just about anywhere you need.
Some problems you could encounter:
If the distance from the trap to a vented line exceeded the code requirements, you could have poor drainage.
The pipe could be smaller than two-inches inside diameter and that could lead to drain problems, besides being undersized for both underground and shower requirements.
When in doubt, consult with the city plumbing inspector or a master plumber.