How do i get mail icon back on macbook after it hot deleted?

Sounds like you moved it from the dock.

Open the application folder and launch Mail. The icon will appear in the dock at the right or bottom depending on where your dock is located. Right click the icon and choose to Keep In Dock or drag it back to the left or top of the dock where you removed it.

Mail should be in the application folder. Make sure you are looking in the main application folder on the hard drive and not in your user account. Some people still have application folders in their user account from previous older versions of the OS. That may not be your case.

Open a Finder Window and search Mail. Be sure you choose This Mac to search in and not your user account. If it doesn't show in the Applications section, then you may have somehow deleted the application. Check your trash and make sure it isn't in there. If it is, right click on it and select Put Back.

If it isn't on the computer, then the only way to get it back would be to reinstall the OS or to find the application on a backup such as Time Machine (if you have a backup) and restore it from there.