Can a Samsung galaxy prime be upgraded from 8GB to higher without adding an SD card? Can a Samsung galaxy prime be upgraded from 8GB to higher without adding an SD card or am I better off to upgrade to a phone with more internal memory? I currently have a 30GB SD card installed and have moved as many apps to it as possible.

Also is there a way to move all my pictures and videos to the SD Card?
Only the most popular phones (e.g. Xiaomi ones) have unofficial storage expansion service, which replaces the eMMC on board with one of a bigger capacity. The quality of the chip and soldering can't be guaranteed, and the replaced original chip could potentially mean private data leak. Don't think twice about this way.

You could move pics and vids to SD card just fine - in fact, doing that is more plausible than moving apps, since many apps can't be moved nowadays.