All junction boxes in use, whether with receptacles, splices, switches or other devices, must be accessible.
This is probably the generally "best" answer. But it may involve significant work, depending on the type of wall. However, not only can receptacles not be covered, junction boxes can't be covered, even if they are only in use for a splice.
If a cable comes down from above, moving the receptacle up is easy.
If a cable comes up from below, you have a problem because you need to extend the existing cable. Normally you do that by splicing in an additional cable in the junction box. But that doesn't help here because now you have a junction box that still can't be covered. There are splices that are approved for in-wall use (i.e., not accessible) which may be an option.
Depending on the type of cabinet, or specifically the type of cabinet back wall, you can:
- Cut a large enough area in the cabinet back to make the junction box fully accessible. Essentially so that there is wall surface visible around the junction box cover plate, so that the junction box is really "in the wall" and not "inside a hole in the cabinet".
- Cut the exact size of the junction box in the cabinet back and add a box extension so that you can mount the receptacles flush with the back of the cabinet. A little more work but will look much more professional.
With typical walls, you could use the receptacles below and it should be very easy to install receptacles above the counter and drop cable down to the lower receptacles. Pigtail each set of 3 wires (in, out, new) in the lower boxes, even if originally they had the normal in on one screw, out on the other screw.