How can I get My Mac Mini mid 2010 back to OS X 10.8.5 or ealier?

I have a Mid 2010 Mac Mini running 10.13.6, but I need to wind it back to OS X 10.8.5. I have the upgrade disks and earlier DVD OSX of 10.6. But none of them will allow a wipe of existing OS and reinstalling of an early OS such as OS 10.7.5 or even the DVD disk of OS 10.6 I have tried to select it as startup disk and it starts to, but then reverts back to 10.13 OS on the drive. I have even tried the Option key at startup and select the DVD but it stops at the selection of it (On the OS 10.6 DVD. I do get to the options table on the 10.7.5 but it needs to have 10.7 or 10.6.3 already on the drive to use as it is only an "update" to 10.75..... I need a DVD or Flash drive with installer somewhere between 10.6.3 to 10.7.0.

How can I find such DVD or img for flash drive or even to burn my own DVD????

HELP Please.