in the sentence "Mother filled the jar with pennies, nickels, and dimes." what would the prepositional phrase be?

The answer is "with pennies, nickels, and dimes".

Explanation:

A preposition is a word that indicates a relationship between other words. Examples of prepositions are: at, in, on, to, for, with, through, etc.

A prepositional phrase is constituted by a preposition and its object (complement). In the structure we are studying here, "Mother filled the jar with pennies, nickels, and dimes", the prepositional phrase is "with pennies, nickels, and dimes". "With" is a preposition that presents several meanings and uses, such as the indication of having someone for company, of possessing a quality, or of carrying or holding something. The object/complement of the preposition "with" is the rest of the structure - "pennies, nickels, and dimes".