If you have made no changes to the ios/ folder, you can just delete it and have Flutter tooling recreate it in Swift mode using
$ cd <parent folder of my_project>
$ rm -rf my_project/ios/
$ flutter create -i swift my_project // Add -a kotlin and/or --org com.some.where, if you did so originally
Otherwise, you can study the differences between the Objective-C templates and the Swift templates using the links below:
The common iOS project template:
That template is instantiated, and then a template specific to Objective-C or Swift is overlaid on top of that:
One notable difference is that you need a
bridging header file in the Runner folder. Remember to add/remove files to the Xcode project, not just the underlying folders.
Hope this helps,
Mikkel