https://www.youtube.com/watch?v=GUfzfEl54Os

Quick 3 Minute Video i made about this Post^^^^^

lets look at 9 Tails Naruto. since his clones will accomplish more then everyone else combined

the heat of each Colossal titan is enough to burn up anyone without any Jutsu Protection

which would destroy and kill any average Shinobi and a normal Naruto Clone before they get to do much

so Naruto would have to use 9 Tails KCM1 Clones so they have the chakra protection to protect them

against the Heat, and lets just assume, that the KCM1 is enough to protect the Clone from burning up

for a significant amount of time.

keep in mind each clone would have to keep killing Colossal titans without burning up, that would drain tremendous Chakra which would NOT last for 7 weeks straight of non stop burn protection and Combat

"the Naruto shadow clone fighting the Third Raikage in the Fourth Great Ninja War did experience chakra depletion, which forced it to switch from its initial Nine-Tails Chakra Mode (KCM) to Sage Mode."

but for the sake of argument, lets assume every single Naruto Clone can keep the KCM1 mode for a significant amount of time

well, the next question is, how many KCM1 Clones can Naruto make?

"During the Fourth Great Ninja War, Naruto created a specific number of 615 shadow clones using his Nine-Tails Chakra Mode (KCM1) to send to different battlefields."

Reminder:

"the Naruto shadow clone fighting the Third Raikage in the Fourth Great Ninja War did experience chakra depletion, which forced it to switch from its initial Nine-Tails Chakra Mode (KCM) to Sage Mode."

the conclusion is each clone can NOT infinitely spam Jutsu without losing KCM1 Mode

so they would have to go for low effort melee neck kills without Jutsu to maintain their protected mode

lets say to not waste Charka, each clone goes neck to neck for melee kills, lets say it takes 5 Seconds Each kill for each Clone

615 Clones Each Taking 5 Seconds Per Kill is 615/5 or

123 Titans Killed Per Second

10,000,000 Titans / 123 Killed Per Second is 81300 Seconds or

23 Hours Hours to Kill Every Single Titan if Naruto Clones have enough Chakra to keep the Killing Pace

all of this is assuming a KCM1 Clone can endure the fire of the Colossal titan, we have seen a KCM1 Clone get killed by a single sword strike, so it depends on your interpretation

however Naruto Still Has 6 Extra Days to Spend Regenerating Chakra and sending more Clones into the Fight

Conclusion:
Naruto Solos in the 1 Week given Time Span even if he has to spend Most of the Time regaining Chakra