a friend gave me a Mac book pro 2009 and it works great, but it doesn't have Garage band on it yet. How do I get the older version?

On OS X 10.11.6 you can either run the newer GarageBand 10 or the older iLIfe version of GarageBand '11, you would need GarageBand 6.0.5.

• GarageBand 10 is only available via the AppStore, and for older Macs only, if you previously have purchased GarageBand and it is associated with your AppleID. If you never purchased it (for free) it will be hopeless. You will need access to a Mac with a current system version, so you can purchase garageBand and associate it with your Apple ID. Do you have a friend or family member with a new Mac, who could give you an user account on the Mac so you could purchase GarageBand there with your own Apple ID?
• GarageBand '11 has been sold initially on iLive DVDs. When your friend gave you the old Mac, did you also receive the Installer DVDs that came with the Mac? Look for GarageBand on these DVDs. You could also look in the Internet for iLive '11 installer DVDs. Perhaps you can still find them at Amazon or eBay. There is hitch - Apple has removed all updaters for GarageBand from their support pages. The update to GarageBand '11 version 6.05 is no longer available at all, the perfect version for your current system. The version 6.0 from the retail DVDs may be too old to run on your current system version. In that case you would have to downgrade to an older system version.

I'd start with the installers that came with your Mac and install the original system version with the GarageBand version that came with the Mac on an external drive and start up the Mac from the external drive with the toriginal system version. I liked the original iLife versions '09 and '11 much more than the current version.

Unfortunately nothing you can do , your Mac it’s to old to run GarageBand