What is scored for bidding and making 3 Clubs Doubled?
The score varies by game variant:

Playing Rubber Bridge:


Above the line - Insult: 50
Below the line - Trick Score of: 120 as 3 * 40


The trick score for the deal equals or exceeds 100, so a game has been bid and made. If this game is the second by the same partnership of the rubber, an additional Rubber Bonus of either 500 or 700 would be scored above the line.

Presumably the disagreement inciting the question is to do with how to score the points earned as doubled - i.e. the trick score above points as 120 - 60. The Rules of Rubber Bridge state clearly:


  Law 72 - Points Earned
  
  The result of each deal played is recorded in points,
  which fall into two classes: 
  
  A. Trick Points: Only declarer’s side can earn trick
  points and only by fulfilling the contract. Only the
  value of tricks named in the contract may be scored
  as trick points (see Law 81). ....
  
  Law 81 - Scoring Table
  
  TRICK SCORE
  
  Scored below the line by declarer’s side, if contract
  is fulfilled:
  
  For each Trick over six, bid and made ... Doubled [in Clubs]: 40
  
  ....
  
  PREMIUM SCORE
  
  Scored above the line by declarer’s side
  
  For winning the rubber, if opponents have won no game 700
  
  For winning the rubber, if opponents have won one game 500
  
  ...
  
  For making any doubled contract: 50
  
  ...


Further down it makes clear that the slam bonuses are scored only for contracts where 12 tricks (small slam) or 13 tricks (grand slam) have been both bid and made.

There are no further premium points scored as there were no overtricks made.

Playing Duplicate or Chicago

(The latter sometimes also termed Four Deal or Party Bridge scoring.)


Not Vulnerable: 470 as 300 (game bonus) + 120 (trick score as above) + 50 (insult as above)
Vulnerable:  670 as 500 (game bonus) + 120 (trick score as above) + 50 (insult as above)


There is a variant of Chicago scoring that makes use of above- and below-line scoring, but that is of no consequence on a hand where game is bid and made (ie trick score >= 100), as here.