Is these a possessive pronoun

No, the pronoun 'these' is a demonstrative pronoun.

A demonstrative pronoun takes the place of a noun, indicating near or far in place or time.

The demonstrative pronouns are: this, that, these, those.

Example: I'll take six of these and two of those.

Note: The Word 'these' also functions as an adjective when placed before a noun to describe that noun. Example: I'll take six of these cupcakes.