To remove DRM form Mobipocket,you just need to Download and install the Epubor Kindle DRM Removal,then follow the guide below to remove DRM from Mobipocket books step by step. Kindle DRM Removal can helps you remove DRM from AZW, PRC, Mobi, TopAZ(.tpz) books with easy, that need you set the "Optional Setting".
Step 1: Run Epubor Kindle DRM Removal, find PID at Mobipocket reader About window.

Step 2: Input PID, select mobipocket book, mobipocket book is saved at "My Document\My eBooks" folder, has .prc file extension. Your PID is the personal key that your reader uses to encrypt and read the file. We're going to need this key if we're to permanently strip the DRM from the ebook.

Step 3: Click "unDrm directory", then remove drm from mobipocket files in the whole folder.
Open your newly created DRM-free kindle file with your favorite application (on whatever device you like). You can use the most professional eBooks Converter software Calibre to convert and manage your ebooks.
Step 4: Convert new mobipocket file to other format ebook using Calibre.
Epubor Kindle DRM Removal Features:
1.One-click removal tool.
2.No quality lose, the same quality as source ebook.
3.No need to backup the source files.
4.The decrypted .mobi files can be supported by most cell phones or other mobile devices
5.The decrypted files can be converted to ePub/PDF/AZW and more