Your camera model requires a minimum of Lightroom 2015.7/6.7 to support the raw files. The only way you will be able to import them into Lightroom 4 would be to use the free standalone DNG converter to create DNG copies that could then be imported and used with the older version of Lightroom.
Lightroom 6 is still available for purchase as a standalone product. However, it is no longer being updated and there will be no more upgrades to the standalone product. It does support your camera after you install the updates that were made available after its original release.
In my opinion, your best choice would be to subscribe to the Creative Cloud photography plan and install Lightroom Classic CC and the latest version of Photoshop. However, this is a subscription option that requires a monthly or annual subscription.