This Script and page takes a statblock in the format seen in most 5e products and parses and converts it to the format used by Open5e.
This works well from many pdfs I have tried.
Here is a statblock you can use to test if you have none handy:
Glabrezu
Large fiend (demon), chaotic evil
Armor Class 17 (natural armor)
Hit Points 157 (15d10 + 75)
Speed 40 ft.
STR
DEX
CON
INT
WIS
CHA
20 (+5) 15 (+2) 21 (+5) 19 (+4) 17 (+3) 16 (+3)
Saving Throws Str +9, Con +9, Wis +7, Cha +7
Damage Resistances cold, fire, lightning; bludgeoning,
piercing, and slashing from nonmagical attacks
Damage Immunities poison
Condition Immunities poisoned
Senses truesight 120 ft., passive Perception 13
Languages Abyssal, telepathy 120 ft.
Challenge 9 (5,000 XP)
Innate Spellcasting. The glabrezu’s spellcasting ability
is Intelligence (spell save DC 16). The glabrezu can
innately cast the following spells, requiring no material
components:
At will: darkness, detect magic, dispel magic
1/day each: confusion, fly, power word stun
Magic Resistance. The glabrezu has advantage on
saving throws against spells and other magical effects.
Actions
Multiattack. The glabrezu makes four attacks: two with
its pincers and two with its fists. Alternatively, it makes
two attacks with its pincers and casts one spell.
Pincer. Melee Weapon Attack: +9 to hit, reach 10 ft.,
one target. Hit: 16 (2d10 + 5) bludgeoning damage. If
the target is a Medium or smaller creature, it is
grappled (escape DC 15). The glabrezu has two pincers,
each of which can grapple only one target.
Fist. Melee Weapon Attack: +9 to hit, reach 5 ft., one
target. Hit: 7 (2d4 + 2) bludgeoning damage.