Hello @pk0018 this is ALWAYS an "it depends" type of answer. There are many variables. Client device types and capabilities with regards to spatial streams and channel width for example, expected client density, what are the primary applications that will be in use, will it require any voice and/or location tracking services, what are the room sizes, building construction, ceiling height, are there neighboring networks/companies, etc, etc. These will all be inputs into your AP placement, density, channel plan, etc.
If it's a typical mix of users, on a typical mix of client devices, running the typical mix of apps with typical EMIX characteristics, we can certainly provide some rules of thumb like an AP per room or an AP per 2500 or 3000 square feet for example. But this is not the best way to plan it out. It might get you close, and AutoRF can close the gap, but some would argue that relying on AutoRF to correct design mistakes is poor planning, and I'd have to agree.
If it's a reasonably-sized enterprise deployment it's always best to have a formal site survey completed, especially if it's your first time doing an enterprise deployment, because it's also an excellent learning process.
For more info on that see my reply in this thread https://community.meraki.com/t5/Wireless-LAN/Should-you-always-do-a-site-survey/m-p/13274
Not sure what kind of space this is, office space, maybe a manufacturing floor or a conference center or exhibit hall? If your back is against the wall and there's no time and no budget for a site survey, and let's assume this is enterprise carpeted office space and conference rooms... Go with an AP per 2500 square feet and/or 50 clients per AP, aim for cell edges at -67dBm with perhaps 20% overlap, set the minimum bit rate to 12Mbps, use dual band with band steering to 5GHz, use 20MHz channels if it's high density, consider enabling/disabling DFS channels depending on your regulatory domain. Depending on the AP placement, you might also consider disabling every other 2.4GHz radio, and might also consider leveraging 2.4GHz for guests for example. Use RF Profiles to restrict 2.4GHz to 5-20dBm and perhaps 5GHz from 8-23dBm for example.
That's all just a shot in the dark without knowing the details. And even if you have floorplans, always ask if there's anything non-standard about the users, their devices, the apps they'll be using, and the building construction and RF environment.
Finally, if you're looking to deploy MR33, also consider your options with the new MR36 APs, since they're new and will certainly be around longer, not to mention get you into the latest WiFi6 technology.
Hope that helps!