Sorry, the motor is rated at 10~12v, 259ma, 7.5 ohm., four wires.
7.5 ohm at 260mA is about 2V, not 10 to 12, and given its 4-wire its likely to be designed for chopper-drive,
so ignore the voltage rating and use the 0.26A as the per-phase current. A chopper drive like the A4988
is the recommended way to go, not an H-bridge, in that case.
But first measure the winding resistance to make sure it actually is 7.5ohm...
Sounds like quite a small motor at 0.5W static dissipation...
One way to avoid the need for a chopper-drive circuit is to use series resistance with the H-bridge. Since
The SN754410 will lose at least 2V, we'll call the supply 10V which means a total of about 40 ohms is needed
per winding, so 33 ohm loads in series with each winding will make it compatible with 12V H-bridge (but will
dissipate 2W each - so use 3W rated power resistors). This technique is the "poor-person's" constant-current