Can I put multiple resistors in series to get higher resistance?
The short answer: Yes. It's the same.


  
  
  The current through resistors in
  series stays the same, but the voltage
  across each resistor can be different.
  The sum of the potential differences
  (voltage) is equal to the total
  voltage. To find their total
  resistance:
  
  
  
  By Wikipedia


But this the ideal value. In the real word, resistors have tolerances and you have take in count. E.g., tolerance of 10%. The final value can vary between 2.7MΩ to 3.3MΩ.