Q: how to copy a movie cd just purchased to my desktop

NOTE: This procedure will not work with copy protected DVD video discs. iDVD, DVD Studio Pro, Disk Copy, and Disk Utility are licensed for reproduction of non-copyrighted materials, or materials you are legally permitted to reproduce.

How to copy previously-burned DVD-R video discs - Apple Support

if the procedure above does not apply because you are trying to use it with copyrighted material it against the TOS of this forum for anyone to assist you here. If it not a copyrighted disk you can convert the file so it can be read by iTunes to share over your account to an iOS device running version 9.0 or greater.

I haven't used it for a while but I recall that Handbrake will make you a file suitable for an iPad.