No you cannot transfer Lowrance Data (.usr) files from your compuer to your iPad, but you can transfer the data if you can get in a Google Earth format.
To convert the Lowarance file(s) (.usr) to a Google I have found a FREE converting program.
Go to http://www.gpsbabel.org/download.html
Once it is installed in your PC, follow the directions to make the conversion, then follow these instructions for installing the Google data into your iPad.
Google earth to iPad
First install Google earth in your iPad or iPhone. Then open the program.
Open your Google Earth in your PC and save the waypoints to a file, preferably a Google KML file.
Once done send your self an email with the saved file as an attachment. Open the attachment file in your iPad then using the out source (the icon representing a document with an arrow pointing upward.
When the option opens select the open in Google Earth. Icon.
All of the waypoints should appear in the Google Eath program on your iPad.
By the way this will also work an any of the Google files I offer in the Captain Paul's Fishing of GPS Waypoints.
Simply substitute the Edge files opened in the PC Google program And them send as an attachment to your iPad.
Google luck, contact me if you need any specific help.