how do i change the type of a field

[Tejo Uppalapati]

Hi, 

There is a field named Raised during. Currently it is as a Text field. I want to have it as a selction of drop down. 

How can I get it done?

[Zachary Hayes]

You'll have to create a new custom field of the drop down type, and migrate data to the new custom field. Going from a text field to a drop down may require you to build scripts to automate the migration.

[Ismael Jimoh]

Sorry this is not possible.
You will need to create a new field and set the values.with the same name, set the option
If you have issues that already use the old field, I’ll suggest euther migrating the value set using bulk edit or removing the old field from the screen.