Renames file extension paths from PNG to JPG. Also Tells the file to search for a folder called "Renamemetopackname" instead of the normal 4k folder.

Blender KB3D PNG to JPG_and_Folder.py

import bpy

for img in bpy.data.images:
    img.filepath = img.filepath.replace('.png', '.jpg')
    img.name = img.name.replace('.png', '.jpg')
    img.filepath = img.filepath.replace('4k', 'Renamemetopackname') #Rename that to whatever you renamed the 4k folder to. ie. CyberDistrict
    img.name = img.name.replace('4k', 'Renamemetopackname') #Rename that to whatever you renamed the 4k folder to. ie. CyberDistrict
    img.reload()
print("Done! Save your blend file!")

#When it's finished make sure everything looks correct and save the blend file with a new name ie > Save-As "Packname_jpg.blend"