https://www.google.com/search?source=hp&q=roland+um-one+mk2&oq=roland+um-one+mk2&gs_l=psy-ab.1.0.0l10.801.11171.0.14660.18.17.0.0.0.0.201.2935.0j16j1.17.0.dummy_maps_web_fallback...0...1.1.64.psy-ab..1.17.2933.0..46j35i39k1j0i131k1j0i3k1j0i20i264k1j0i46k1.0.z3XXy0sXemg

link was for the Roland Ume-One midi to USB cable working perfectly for me

Note that the option for a cable that has MIDI 5-pin (round) DIN connectors on one end and a USB type-A (rectangle - older USB 2.0 and early generation USB 3.0) is an option although unnecessary under most situations.

Some "Mac Laptops" do not have a USB type-A connector such as the latest generation Macbook Pros. If you do have a USB type-A connector, then all you should need for the MIDI connection is a certified USB 2.0 type-B (more of a square connector) to USB 2.0 type-A connector. These are commonly known as "printer cables" for modern printers. The type-B connector fits into Montage's "USB Host" port. For this connection, ensure your Montage is set to USB midi mode (top status line of touchscreen should show the USB icon:

Instead of the MIDI connector (round jack) icon:

And your Mac should have the latest Yamaha Steinberg USB Driver installed:

https://usa.yamaha.com/products/music_production/synthesizers/montage/downloads.html

Any USB cable I would recommend purchase from a major manufacturer to ensure the USB sig certification (for high-speed use) is legitimate and strive to find one known to be shielded. These will tend to be the more expensive ones - although price alone is not an indicator. Strive to get the shortest cable which will span the distance between your computer and keyboard.

I cannot determine the length - but something like the Tripp Lite U023-006 (3ft version is U023-003) satisfies other bullet items except clear indication it is certified (no logo which is common).

Belkin cables typically have the USB cert logo on the packaging and feature shielding. These can be found even at your local box stores (variety of sources).