It is no longer possible to get an iPhoto Version, that will run on El Capitan. It is too late now. Even if you manage to find an old iLife '11 CD at Amazon or eBay; it will not possible to update this iPhoto'11 to iPhoto 9.6.1, the only iPhoto version that is compatible with El Capitan. This update has only been distributed by the App Store and is no longer available, unless you have previously purchased it from the AppStore.
But the Photos.app on El Capitan will be able to migrate an iPhoto '09 (v8.1.2) library to Photos and create a Photos Library from it. Just make sure, the iPhoto Library is in a ship-shape condition, before you upgrade to El Capitan and can no longer run iPhoto. You may want to create a backup copy of your iPhoto Libraries, then run the iPhoto Library first Aid tools on the library to repair the permissions and the thumbnails, rebuild the library.
Photos will create a new Photos Library from your iPhoto Library, when you first launch it. The new library will be created in the same folder as the iPhoto Library. It is important, that your iPhoto Library is on a volume, that is compatible with Photos. The Pictures folder would be the best place, if have enough storage on your System volume.