Use the free tool DNGCONVERTER from Adobe to convert your .CR3 to dng and being able to import them in Lr 5.2
Buy a 20GB Photography plan (which includes Lrc Licence, as well as a Photoshop licence) on the Adobe site, then install LrC on your computer. With LrC, open your 5.2 catalog, it will be automatically converted to the 12.5 format. Then you will have access to all the content of your catalog with LrC.
Use the free tool DNGCONVERTER from Adobe to convert your .CR3 to dng and being able to import them in Lr 5.2
Buy a 20GB Photography plan (which includes Lrc Licence, as well as a Photoshop licence) on the Adobe site, then install LrC on your computer. With LrC, open your 5.2 catalog, it will be automatically converted to the 12.5 format. Then you will have access to all the content of your catalog with LrC.