Why don't we use köpeklar here?
The number 42 already says that there is more than one dog. So Turkish doesn’t have to mark the noun as plural, redundantly.
I said 'burda 42 köpek var' it is true i am sure but it said wrong
there is no word that means "burada" in the English sentence
To add to what Selcen Hanım said, "there are ..." = "... var". Both words together have the "var" meaning; there is no location information here.