Thank you for your post.
Bento 4 for iPad will only download Bento 4 Template files. If a Template file was posted in a Bento 3 format, then Bento 4 for iPad will be unable to install it.
Which Template files are you trying to download? I'll have the person who manages the Bento Template Exchange to contact the author and see if they plan to update it to Bento 4 format.
In the future, since you posted your question to the FileMaker Pro forum, please post Bento questions to the Bento forum at: