Both the JT and SLDPRT CAD files are fairly common, so at least some of the dedicated CAD translators should be able to perform this type of conversion. Probably same can be achieved with some exchange format that is easier convertible to SolidWorks SLDPRT.
Convert JT Open CAD 3D model format to SolidWorks CAD part.
We found 2 software records in the database related to .jt to .sldprt file format conversion.
Microsoft Windows software - convert jt to sldprt on Windows
A CAD converter with huge format support
Convert from jt file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned jt to sldprt. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A CAD visualizaton, analyzation and translating system