Because he knows that Naruto strength is not like when fourth shinobi world war where Hokage at that time still had Kurama or Kyuubi.

Now Naruto is not jhincuriki of nine tailed fox, that why Amado thinks that with Naruto current condition, Naruto probably won’t win against Code, even though Sasuke will join him in fight.

Because Sasuke also lost Rinnegan eye which functions to reverse objects, reverse himself and can even open time and space portals.

It is known that when Naruto and Sasuke fight together, their strength can overwhelm enemy.

However, current situation for two shinobi was different, in that their strength was reduced due to loss of what they had before.

According to theory from Cilacap.info, Amado is like Orochimaru, if Orochimaru can do edo tensei, then Amado can make clones of dead people.

Therefore Cilacap.info theorizes that Amado will create a clone of a Shinobi.

Here are strongest Shinobi clones that Amado might create:

1. Hashirama Senju

The first Hokage is known to be quite strong, even though his opponent has Sharingan which for anyone is quite dangerous. But Hashirama managed to defeat Madara Uchiha.

2. Uchiha Madara

Although in fourth shinobi world war Madara is known to have evil ambitions, but finally he realized before dying.

Uchiha Madara strength might be able to help Konoha to deal with Code.

3. Minato Namikaze

Maybe this fourth Hokage clone can also compensate for technique than Code which is known that Code can also move places quickly with technique of marking place with his claws.

Such is theory that Amado is likely to come up with.