First look at you sure winners : one in spades, three in hearts and two in Clubs : a total of 6 winners. You therefore need to develop three more winners to make your 3NT contract.
Your best chance of course is the Diamonds suit. Once Opponents' ♦A is gone you will have 4 more winners.
But this means giving one of the Opponents the lead once more with his ♦A, and after winning that trick he will immediately continue to play spades again and play out all spade winners.

Wrong play
If you play the ♠A from Dummy on the very first trick there is a good chance that you will not make your 3NT contract.
If the 8 spades of the Opponents are divided 4-4 there will be no problem, because they will only make 3 spade tricks plus the ♦A, 4 tricks in total, leaving you with the required 9 tricks to make the 3NT contract.

But if Opponents' spades are divided 5-3, they will make 4 spade tricks (instead of 3), plus their ♦ A : 5 tricks in total and the 3NT contract will go down one.
(South will win the first Diamond trick with his Ace, then immediately return a spade to North's 4 spade winners.)

Right play
Instead you should play the ♠7 from Dummy on the first trick, and when North follows up (next trick) with the ♠Q, Dummy once more should play low : the ♠8. Only on the 3rd trick should Dummy play the ♠A !!
This is called a "hold up" play : you are holding up playing Dummy's Ace.   For look what has happened :

When after winning the ♠A Dummy leads a diamond to chase out South's ♦ A, South has no longer any spades left in his hand to lead back to his Partner.
North is stranded with two more spade winners in his hand but can not gain the lead. For whichever suit South now leads (at trick 5) Declarer or Dummy will win the trick and can cash in all remaining tricks as winners (making 10 tricks instead of only 8).

If North had been holding both 5 spades and the ♦ A instead, the contract was doomed from the start. But good play is all about playing the percentages, so that every time that the favourable distribution occurs (like in this game) Declarer will be ensured to make his contract.

Whenever you are in a NT contract and you hold 5 cards in a suit with only the Ace as a stopper (xx opposite Axx) : hold up twice !