Here is the full list of all 35 A Plague Tale: Innocence achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Find all curiosities
Find all the flowers
Fully upgrade the equipment
Fully upgrade the sling
Find all the gifts for the orphans
Find the tomb
Save a soldier
Find a lunch for Hugo
Complete the aiming training
Complete all chapters
Complete chapter 16
Find Rodric's forge
Enter into the 5 alchemist carts
Complete chapter 15
Complete chapter 14
Stay with the captain
Complete chapter 13
Complete chapter 12
Find 6 flowers
Find 13 curiosities
Save the dying
Complete chapter 11
Complete chapter 10
Craft 100 ammunitions
Complete chapter 9
Enter through the main door
Complete chapter 8
Complete chapter 7
Complete chapter 6
Complete chapter 5
Complete chapter 4
Play hide-and-seek
Complete chapter 3
Complete chapter 2
Complete chapter 1