My son's college financial aid office asks me to submit Form 1065 for Schedule K-1 for 2021 year but I do not see 1065 in my 1040 while Schedule K-1 is shown. What to do?

You don't fill out the 1065.  The fund or broker does.  You get the K-1 from the 1065.  They probably just want to see the K-1.

If those funds are structured as partnerships, you should have gotten a Schedule K-1 for each fund. In the top left corner of the Schedule K-1 it says "Schedule K-1 (Form 1065)." That's the form that the financial aid office wants. It's Schedule K-1 for Form 1065, not Form 1065 for Schedule K-1.

Form 1065 is the partnership's tax return. You wouldn't have a copy of it. The partnership sends it to the IRS, just like you send your Form 1040 tax return to the IRS. The partners never see the Form 1065.

There's a surprising amount of ignorance and misinformation about tax returns among the staff in college financial aid offices. They know a lot less about taxes than they think they do. If they give you a hard time or make unreasonable requests, ask to talk to someone who knows more about tax returns.