What is correct in a sentence knowledgeable or with?

Neither "knowledgeable" nor "with" is inherently correct or incorrect in a sentence; it depends on the context. They are different parts of speech and serve different grammatical functions.

* Knowledgeable is an adjective. It describes a noun. Example: "She is a knowledgeable professor."

* With is a preposition. It shows a relationship between a noun or pronoun and another word in the sentence. Example: "She went to school with her friends."

To know which is correct, you need to provide the sentence you're working with.