jpeg to tns conversion is related to transferring pictures (.jpg, .gif, .png etc.) to TI-Nspire product line is a series of graphing calculators developed by Texas Instruments. It is actually possible that only certain pixel sizes of the pictures can be transferred, so you may need to resize the file first.
You can find a software provided by TI that allow users to transfer texts, pictures and other documents to your calculator devices. It is also possible that other small utilities can be found on various Nspire sites community websites.Open JPEG file Open TNS file