Combining codes for 3 sensors
In general:


There can be only one setup, in most cases you can put the code from all three setup's together, but checkout the code does not interfere, i.e. does not use the same pins. In that case, change the pin numbers if possible (and change the circuit accordingly).
For the loops it can be more tricky:


Check how often each loop should be called. If one loop costs e.g. 500 ms that means the other loops will be called less often, which can affect the precision or even good readout of the sensor.
If all loops are relatively small and the duration do not matter, you can just call them after each other (rename the loops and call them one by one).
If there is a time constraint, than split the lengthy loop in a small part, and call it whenever needed. There is no clear rule for this.



What you can try is:


Check for reach loop how long it takes
Than for each loop add a delay with same time as the other loops, thus:


Test the duration (average) of loop 1, than of loop 2, than of loop 3. Assume loop1 takes 100, loop2 200 and loop3 300 ms.
Test loop1 without calling loop2 and loop3, but just add the delay (200+300=500 ms).
Check if it works, if so, it means you can call the other loops without problems.
Do the same for loop2 (with 100+300ms delay) and loop3 (100+200ms).
If all loops work correctly, than you can call the loop1, loop2, loop3 in sequence.
If not, you have to call the loop(s) that do not work either more often or in a different way.