You want to trade a PS4 key for The Crew with a PC key? If so, I highly doubt it's possible. See if you can get a refund on the PS4 key if you haven't activated it yet. Then use those fundes to get a key for the PC.
If you've activated your key there's no way they will refund or exchange it for you.
There is no way to exchange keys after purchasing. I would suggest contacting the retailer if it was a mistake. Feel free to contact the Support team if you have any further questions.