First of all, we’d like to clarify that it is not basically preferable to repeat `Umrah in one traveling. However, there is nothing wrong to perform multiple `Umrahs in one traveling if there is a reason for that such as performing `Umrah for oneself and on behalf of a father, a relative, etc.
In case of performing multiple `Umrahs in one traveling, after finishing the first `Umrah you have to get off ihram via shortening or cutting your hair. Then, you have to go to At-Tan`im where you can intend the second `Umrah and wear ihram to start the rituals of the second `Umrah. After finishing the second `Umrah you have to get off Ihram via shortening the hair and then go to At-Tan`im for the third `Umrah.
Having clarified the above, it is preferable to shorten one’s hair in the first `Umrahs and to shave it if one likes in the last `Umrah. As for the hair that should be cut, the basic ruling is to take from all parts of the head.