Maya list all texture of all Udim
py
import maya.app.general.fileTexturePathResolver as ftpr
nbOfUdim = ftpr.findAllFilesForPattern(file_path, None)
path = mc.getAttr(file + ".fileTextureName")
uvTilingMode = mc.getAttr(file + ".uvTilingMode")
pattern = ftpr.getFilePatternString(path, False, uvTilingMode)
nbOfUdim = ftpr.findAllFilesForPattern(pattern, None)