How Do I Get My Psp To Read The UMD Disk?

You can attempt a replacement of the components if that proves necessary. There are many sites on the internet where you can order replacement parts, but I'm not gonna lie to you... Disassembling a PSP down to that level is a tricky business. I tore one down to the point where I was able to solder closed a permanent circuit to fix that fact that a friends' WAN switch had broken off the circuit board and it was really tricky... But it can be done, and my friends' PSP still works like a champ.
Now, it's up to you, but you may just want to start by trying to figure out where the problem seems to stem from... Can you hear/feel the UMD spinning up when you try to use it? Did you drop it before you started having this problem? Can you feel the read head moving back and forth trying to read the disk?
If everything seems to be ok, so far as movement within the system, it may just be out of alignment. Look in through the UMD door and see if the laser lens seems straight and looks like it's mounted correctly. If not, you may be able to just open it up, tear it apart (you will have to) till you can get access to the laser lens assembly and see if you can re-align the laser to where it seems like it was supposed to be, and that may fix it. Just make sure you make every effort to not lose any parts, keep dust out as much as you can, touch something metal that is grounded (like your pc case) before you work on it, and find some way to remember where everything goes... There will be a fair number of parts, and screws and they will ALL need to go back where they came from.
Hope this helps, and good luck!