Do you mean convert a 2-dimensional (flat) video to a 3-D experience (for 3D VR headset, etc)?
If you just want to convert normal videos to view non-3D videos on your headset, then sure, but they won't be 3-D. Video has to be created as 3D, and your iPhone has no capability to record 3D videos .
Some video converter can help your convert normal video to 3D SBS format. Search on Google by using VR video converter. I don't know why they can achieve this, but I just convert my video to VR format because my father bought a Samsung Gear for me.