Due to certain properties assigned to devices based on the type, it is not possible to simply change the device type once assigned.
Quickest way will be to :
1. export the device records from actions menu by doing a "re-importable export for selected devices".
2. After you export the info, you can bulk delete devices from action menu.
3. Change the excel file to reflect blade devices and new hardware model(if applicable)
4. And then re-import it from Tools > Imports/Exports.