using wallet without credit cards

Yes, you can do that.

You can search the phone as a whole:

Use Search on your iPhone, iPad, or iPod touch - Apple Support

Or go to the App Library by swiping past the last Home Screen.

where can I find wallet on my phone.

Use App Library to search Wallet app, see this Apple article:

Organize the Home Screen and App Library on your iPhone

Organize the Home Screen and App Library on your iPhone - Apple Support

If you have find the app, tap on the app (don’t open the app), then drag to the Home screen & drop it.

See this Apple article: Add, use, and share boarding passes, tickets, and other passes in Apple Wallet

Add, use, and share boarding passes, tickets, and other passes in Apple Wallet - Apple Support

You'll have the option to add a Credit Card, Debit Card, Apple Card, or transit card in certain cities, so that depends on your country.