Check this post:
COntains MTBF for 100, 250, 450.
For the rest it seems you need to contact support.
Here are the MTBF values:
Could someone provide me the MTBF for MX 68 and MS 210 and is there a public document that has published MTBF for these products so that I can share with my customer.
Unfortunately, there is no public-facing document available. However, you can always open a case with Meraki support to get this information. Please find the requested MTBF values below.