How can I tell If I have a Version 4 or higher?
 

I read some place that if the bottom of my PS2 has 8 screws it is a version 4 or higher. Mine only has 8 that I can find. I also read that if the serial number started with U4 it was a unit 4. The number on the back is SCPH-30001. Is this enough info for me you to tell me what I have so I can get the new PS2 DVD modchip? Thank you

As it happens, yours will be a v4 based on the description. That's an opinion not a guaranteed fact!

v4s had serials U3/U4/U5/U6