@doeadeer , No problem,
your raspberry 3 will do the job for the google assistant project and the mirror, don’t worry.
For the download just click on the file aiyprojects-2019-11-13.img.xz and flash it on an sd card (remember to format it in FAT32 before).
Afterwards I leave you to look for tutorials to install the different programs (google wizard, magicmirror, etc.)
Hoping that everything will go well ;)
Creatib