Connecting unused input 74LS07 gate
See Section 6.5 of the data sheet you linked. Iih and Iil are the numbers you are looking for.

Iih is the input current when the input is held high (nominally 2.4 volts for TTL/LSTTL) and in this case is 20 uA.

Iil is the input current when the input is held low (nominally 0.4 volts), and in this case is -200 uA. The "-" indicates that current is flowing out of the input, and you need to sink this current, rather than source it.