I am assuming you’ve PHPMYADMIN , not going in detail as to how you install that and all that crap
First identify the attribute id of the is_anchor attribute:
SELECT * FROM eav_attribute where attribute_code = 'is_anchor';
I get attribute 54 as my query not sure what you will get as that’s all depends on your environment
Now let’s run a Query to update all category to Anchor YES
UPDATE catalog_category_entity_int set value = 1 where attribute_id = 54;
TADA !!!!!!