I think you don't need a pronoun if we understand pronoun as "a word that substitutes a name "
You don't need it because you are not substituing a grammatical subject "he/el, she/Ella, we/nosotros" (presonal pronouns/pronombres personales)
You don't need it because you are not saying something is of your property or belongs you (possessive pronoun/ pronombres posesivos) "mine/mio, yours/tuyo"
You don't need it because you are not expressing distance you and a point "this/este'" (demonstrative pronouns/pronombres demostrativos)
You don't need it because you are not indicating an defined quantity in an imprecise way "either/cualquier , few/pocos" (presonal pronouns/pronombres personales) or expressing order/ quantity precisely ( first/ primero, one/ une, two/dos) ( numeral pronouns/ pronombres numerales)
You don't need it because you are not introducing a question or exclamation "what/ que, what is that thing?/ Que es aquella cosa? " (/pronombres intereogativos o exclamativos)
You don't need it because you are not introducing an adjective sentence "that/que, wich/que/cual, who/que/quien, whom/que/a quien, whose/cuyo,"
(Relative pronouns/pronombres relativos)
I am not a teacher but I'm pretty sure this is correct