Needing to link 2 x MS120-24P switches via SFP using fiber - they will be about 120ft from each other. We'll be using the Meraki "1 GbE SFP SX Fiber Transceiver". What kind of fiber do I need to buy for this to work? Is there a reference guide or something somewhere that I can't seem to find on this?
The grade of the fibre you would need is called OM3. From memory it is coloured "aqua".
If sometime in the future you think you might want to upgrade to 10Gbe then you should probably splash out on OM4. OM4 is raspberry pink.
I typically use OM4 for everything these days unless I get push back on the price.
For that length you could get away with using a long fibre patch lead if you can run it safely without it being kinked or damaged in anyway. If not get a cabler to run a proper fibre link with patch panels at each end. The second option will be more expensive but will be more reliable.