Check device’s RAM and storage via serial number

You can enter your serial number here -> Check Your Service and Support Coverage - Apple Support and it will tell you the model of the Mac that has that serial number. It will be something like this:

iMac (Retina 5K, 27-inch, 2019) <- this is the model

Purchase Date: July 2020

Serial Number: XYZ.............

Then you can look up the model to get the original tech specs including RAM & storage at ->

Mac Manuals and Downloads - Apple Support or

Everymac.com

If the RAM or storage was upgraded after purchase, the only way you can get that information is via About This Mac > System Report, as I indicated in my earlier post.

You can get basic information about your Mac from the Apple menu  in the corner of your screen. Choose About This Mac. For more detailed information, then click System Report. On the resulting screen you can find info about RAM & storage under Hardware > Memory and Hardware > Storage

Tech specs on all the Macbook models are available here. Note, however, these are only specs for models as delivered by Apple; if additional RAM or storage was added after purchase, that will not be shown here.

By any chance do you know the model number?