I have several books but they are in APK format and I have no Idea how to convert them can anyone help me with this?
APK format is basically a zip file. You will not be able to directly convert it to PDF or EPUB.
Just rename it to filename.apk.zip
and unzip it like you would do to a zip file to access the files inside.
You can also open it using 7Zip, it's a free tool. Download it here:You are not allowed to view links.
Then Right click the .APK file, Select 7-Zip, and select Open Archive.
Let me know how that works for you.