If you clarify and what you’re trying to achieve (e.g., sideload on own device, distribute to testers, reverse‑engineer an app), I can give you a precise, actionable path forward.

You might need to select a developer or distribution certificate. If you are just testing, a development certificate will work. Make sure you have a valid provisioning profile associated with your app.

If you frequently need to perform this conversion, consider these professional tools: