I want to change the "Select a field type" from multi line text to a checkbox. How do I do this ??

[Gary Moran]

I  want to change the "Select a field type" from multi line text to a checkbox. How do I do this ??

[Sajit Nair]

Hi @Gary Moran , 
I don't think you should be doing that.
You can maybe switch from similar type ones (Like single select checkbox to multi select) but not from multi line text to checkbox but even that is not advisable unless you are fing touching up your db and risking data issues.

Read more here - Link 

I would suggest, create a new field and take bulk export from existing one and bulk update to new one.
Let us know if you need any other help with that.