1. The instructions says:
“If you previously held or currently hold J-1 (principal) or J-2 (dependent) nonimmigrant exchange visitor status, you must submit copies of all relevant Forms IAP-66 and/or Forms DS-2019, Certificate of Eligibility for Exchange Visitor (J-1) Status, ever issued to you (if available). You must also submit copies of all available J-1 or J-2 nonimmigrant visas issued to you, and copies of all available Form I-94 and passport pages with entry stamps showing your admission to the United States in J-1 or J-2 status.”
However, if you no longer have those or cannot locate them, there’s really nothing you can do in that case but to file as is and hope no issue gets raised about not submitting those documents.
2. While the current I-94 is important for demonstrating one entered the country legally, it doesn’t hurt to have the past I-94s also (at least having them on hand for when you go for your interview) as those are one of the ways of demonstrating continuously maintaining a lawful presence in the past.
p.s. I hope your J visa wasn’t subject to a 2 YHRR, or you’ve completed or obtained the required waiver if it was.