@Jayanth Rajanna Yes for unmanaged disk, you just need to copy the disk between storage accounts, move from Premium storage to standard storage and it becomes SSD to HDD.
Hope this helps! Kindly let us know if the above helps or you need further assistance on this issue.
----------------------------------------------------------------------------------------------------------------------------------
Please don’t forget to "Accept the answer” and “up-vote” wherever the information provided helps you, this can be beneficial to other community members.