How can I find out what my passcode is? I’ve never had to use until now.

Do you mean your Apple ID password right? Not your iPhone passcode!

if you still remember what is your Apple ID password see this article to learn how to change it ☞ Change your Apple ID password - Apple Support

but if you forgot it See this article ☞ If you forgot your Apple ID password - Apple Support

If your passcode.

See the Apple Support article(s) below for IOS 15.2 or later..

Passcode - How to reset your iPhone, iPad, or iPod touch when you forgot your passcode (IOS 15.2 or later).  *

ASC YouTube for how to restore your iPhone if you forgot your passcode - Apple Support.  -

See the Apple Support article(s) below for earlier than IOS 15.2 . 

Passcode - If you forgot the passcode for your iPhone or your device is disabled.    *

See the Apple Support article(s) below for earlier than IOS 15.2 . 

Passcode - If you forgot the passcode for your iPad or your device is disabled.     *

Try the following:

▷ Forgotten iPhone Login Passcode.

Need more help?

• Call Apple Support at 1-800-APLCARE.
• International Support.
• Contact Apple Support.
• Chat using Messages.