It depends on the monitor. Exactly what monitor are you looking at? Is it new?
A new monitor will come usually with an appropriate cable.
Some 30" units will be 1080P or 1920 x 1080 resolution.
That is the usual for a TV.
Others will be 2560 x 1600 and require a dual link cable.
Others may require HDMI or displayport.
Some will have multiple options, others only one connector type.