The lambda sensor is an unknown for us. It looks like perhaps you give it 7.5V excitation and it then provides a +/-2mA signal, but other language on the datasheet makes me think it is not that simple, including:
"This lambda sensor operates only in combination with a special LSU-IC"
... which makes it sound like the sensor is very special and requires a special IC to excite it and measure from it. If you do research and get to the point where you can read the sensor with a DMM, then we can translate that to how to read with a LabJack.
For the first rpm sensor, you would have to provide a 12V supply and then it provides 7mA when low and 14mA when high. You would need a load resistor, and then also a comparator IC to get a nice voltage pulse signal.
The second rpm sensor looks better. You can just give it 5V from the LabJack and it outputs a voltage pulse that will connect directly to a digital input.
Once you have an RPM pulse train, you will use a counter or timer to count or time the pulses in hardware, so you do not have to read from the LabJack fast.
The sensor you linked has an I2C output. The LabJack can talk I2C, but I would consider it an advanced topic so if you are not comfortable with I2C I suggest a different sensor.