Product prioritization

Should he write user stories for each backlog item? Or is this something he does during sprint backlog meeting 

Should write acceptance criteria for each item? Is this something he does during sprint backlog meeting?

I assume you mean Product backlog refinement session in above questions. Why do you think its PO's responsibility ? 

From Guide -

The Product Owner is the sole person responsible for managing the Product Backlog. Product

Backlog management includes:

• Clearly expressing Product Backlog items;

• Ordering the items in the Product Backlog to best achieve goals and missions;

• Optimizing the value of the work the Development Team performs;

• Ensuring that the Product Backlog is visible, transparent, and clear to all, and shows what the Scrum Team will work on next; and,

• Ensuring the Development Team understands items in the Product Backlog to the level needed.

The Product Owner may do the above work, or have the Development Team do it. However, the

Product Owner remains accountable. 

Should he come with story points for each item? Or can this be done during backlog grooming?

Why PO should come up with estimates ? As per guide - 

The Development Team is responsible for all estimates. The Product Owner may influence the Development Team by helping it understand and select trade-offs, but the people who will perform the work make the final estimate.

Should he write user stories for each backlog item?

Does the Scrum Guide say anything about anyone having to write user stories?

Or is this something he does during sprint backlog meeting 

The Scrum Guide says: "The Product Backlog evolves as the product and the environment in which it will be used evolves. The Product Backlog is dynamic; it constantly changes to identify what the product needs to be appropriate, competitive, and useful."

Should write acceptance criteria for each item?

Does the Scrum Guide say anything about anyone having to write acceptance criteria?

Is this something he does during sprint backlog meeting.

The Scrum Guide says: "Product Backlog items that will occupy the Development Team for the upcoming Sprint are refined so that any one item can reasonably be "Done" within the Sprint time-box. Product Backlog items that can be "Done" by the Development Team within one Sprint are deemed "Ready" for selection in a Sprint Planning."

Should he come with story points for each item?

Does the Scrum Guide say anything about anyone coming up with story points?

Or can this be done during backlog grooming?

The Scrum Guide says: "Product Backlog refinement is the act of adding detail, estimates, and order to items in the Product Backlog...The Development Team is responsible for all estimates. The Product Owner may influence the Development Team by helping it understand and select trade-offs, but the people who will perform the work make the final estimate.