How can I convert large stp file into solidworks ?
SolidWorks nowadays has two modes for importing STEP files:
1. 3D Interconnect switched ON
2. 3D Interconnect switched OFF
Since it is a large STEP file, I expect 3D Interconnect to accelerate initial opening of the STEP file. But if you want to adjust the geometry, you should then save the model and then RMB + Dissolve.
However, depending on the size of the STEP file, it will take a long time to load regardless. If your STEP file is 500 MB you should expect more than 10 minutes loading time, easily. I Have seen STEP files of 1.5Gb open in no less than 30 minutes, usually more.
The factors to speed up STEP file opening:
-Have the STEP file on your local disc, not on a network location or external drive.
-Have enough RAM and a fast CPU (high single thread performance, mostly).
-Use SSD drives, not HDD drives. Preferably with NVMe instead of SATA interface.
Finally, in Tools > Options > System options > Import, don't have 'Import sketches' switched on.
Other than that, there is not much else you can do. Just try and open it, and go get something to drink...