I'm replacing a core support on my car I only have a mig welder and was planning on plug welding the 4 spot on the top but for the one spot welds that runs vertical can I still plug weld those in or no since it's running vertically

Sorry nobody answered you sooner.
No it shouldn't matter what direction the weld is going, horizontal or vertical - especially for plug welding. A standard weld bead is a lot harder going vertical than horizontal, however.