Your best bet is to:
1. Consult your owner's manual: This is the most reliable source of information. The diagram should show the fuse box layout, identifying the starter relay.
2. Check the fuse box cover: The inside of the fuse box cover often has a diagram showing the location of fuses and relays.
3. Look for a relay that's labeled "START" or has a symbol depicting a starter motor. The relay will likely be a relatively large one.
If you can't find it using these methods, a search online using "2001 Chevrolet Venture starter relay location [engine size]" (replace "[engine size]" with your engine's displacement, e.g., "3.4L") might yield more specific results, including images from other Venture owners. You can also consult a trusted mechanic.