Is from a pronoun?

No, the word 'from' is a preposition, a word that shows a relationship of a noun or pronoun and another word in a sentence. The preposition 'from' indicates a source, origin, or beginning of the object of the preposition.

Examples:

It's a letter from mom. (the preposition 'from' connects the object of the preposition 'mom' to the noun 'letter')

It was sent from Florida. (the preposition 'from' connects the object of the preposition 'Florida' to the verb 'sent')

A pronoun is a word that takes the place of a noun in a sentence.

Example: Here's a letter from mom. It was sent from Florida. (the pronoun 'it' takes the place of the noun 'letter' is the second sentence)