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
Enter into the 5 alchemist carts
Save the dying
Fully upgrade the sling
Enter through the main door
Find all the gifts for the orphans
Find a lunch for Hugo
Stay with the captain
Complete all chapters
Complete chapter 16
Find Rodric's forge
Complete chapter 15
Fully upgrade the equipment
Complete chapter 14
Complete chapter 13
Complete chapter 12
Complete chapter 11
Complete chapter 10
Find 6 flowers
Complete chapter 9
Complete chapter 8
Find the tomb
Complete chapter 7
Craft 100 ammunitions
Find 13 curiosities
Play hide-and-seek
Complete chapter 6
Complete chapter 5
Save a soldier
Complete chapter 4
Complete chapter 3
Complete chapter 2
Complete chapter 1
Complete the aiming training