I have older version ipad. If I buy the ipad pro, will there be problems transferring info from icloud backup.

Old iCloud backup? Can't you backup your old iPad just before transfering data from the old device to the new one?

Keep in mind that "restoring from backup" procedure overwrites all data, so it's better to use a recent backup, if possible.

These are the instructions:--> Restore your iPhone, iPad, or iPod touch from a backup

Regards

Giulio

Restoring from an iCloud or iTunes backup isn’t the only option...

These support pages should get you started with setup of your new iPad - and the methods of transferring your data from old to new iPad:

Set up your iPhone, iPad or iPod touch – Apple Support

Transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support

Use Quick Start to transfer data to a new iPhone, iPad or iPod touch – Apple Support