IUPAC name of the compound is
1,4-dimethyl-2,5,8-triChloronaphthalene
1,4,7-triChloro-6,8-dimethyl naphthalene
2,5,8-triChloro-1,.4-dimethyl naphthalene
1,4-dimethyl-3,6,9-triChloro naphthalene
As per lowest sum rule and alphabetical order of substituents.