Can you be a little more specific as to what you are trying to do? LinuxMCE 0810 is quite old at this point and I'm not sure what SlimServer versions may be available for it. The RaspberryPi setup for squeezeslaves/squeezelites is documented quite well in the raspberrypi.org forums, but I find it hard to search for things there.
Do you have a core running LinuxMCE 0810 already? (This is quite old, we recommend 1204 even though it is listed as alpha)
Where are you planning to run the multiple sound cards? How many?
Is this one or more RPis? (1xrpi with 2 usb cards, 2xrpi with 4 usb cards total)
Under LinuxMCE 1204 you can easily pxe boot RPi1 devices or sd boot RPi2 devices. When creating the devices in linuxmce it will ask what you want to do with them and allow you to choose "Squeeze" which will automatically run a single squeezelite device on that rpi and setup the necessary items on the core. Multiple squeezeslave/lite devices can be added to the RPi in the linuxmce device tree (and MAC addresses adjusted to not overlap). After that you can go to a linux terminal and run 'squeezelite -l' which will list the sound cards that are detected. You block and copy the name of the card you wish to use into the LinuxMCE webadmin, reload the dcerouter on the core and reboot the RPi. This will bring up the squeezelite devices and ensure they are linked to the slimserver (what is now Logitech Media Server).
To do this on LinuxMCE 0810 will take a lot more manual setup.