How do I get my Gmail over to this phone from my old phone?

..Also there's 'google app' for Gmail, in the Apple app store for iPhone/iPad..

Rather than set up Apple Mail for only one or two gmail accounts, I use this.

‎•Gmail - Email by Google on the App Store

https://apps.apple.com/us/app/gmail-email-by-google/id422689480

Gmail: Private and secure email at no cost | Google Workspace

https://www.google.com/gmail/about/

Their App sees updates from google; & accesses Alpha/Google details. Or Login

from any browser/device, & bookmark that ~ as a backup means to access gmail.

[For those seeking to use gmail in business, see link to 'secure and private' gmail.]

Does the gmail account appear in the mail app? If not, add the account to the app.

Add an email account - Apple Support

IIRC, After you do that, when you tap on the inbox, you will have to authenticate with your password and you will get a code to enter for verification. After that, all of your mail folders should load and your emails will sync to the new phone.

When you get a new phone, the easiest way to migrate all of your data, including mail accounts to the new phone is to use Quick Start.

See this link to see how --> Use Quick Start to transfer data to a new iPhone or iPad - Apple Support