1. Save the .deb file in a folder and Right Click it. Select 7-zip and click Extract Files in the next menu.
2. Now click OK on the next window and it will start extracting the contents of .deb file.
3. Open the resulting Folder and you will find data.tar file inside. Simply extract data.tar file with Right Click > 7-zip > Extract Files.
4. Now you should have data folder and data.tar file in the folder. As shown in the image below.
5. Go inside the data folder and now open Applications folder. Here you will find a folder ending with .app name. As I have Kodi.app folder in the image attached below
6. Drag the .app folder into the Payload folder.
7. Next you have to Right-click the payload folder and Click 7-zip > Add to archive option.
8. A new window will pop up. Here you have to make sure that the Archive format is set to zip and name the archive ending with .ipa . The name doesn’t matter, just make sure that it ends with .ipa as shown below. After that click OK.
Then your done.
Credits: Drgeeky