How to change column length in table sales_order

I’m new to Magento. I want to store 3rd party order id and customer id in column ext_order_id and ext_customer_id in table sales_order.

Problem is these 2 columns has length 32, so I altered the table to set it to 50. However, every time I ran command bin/magento setup:upgrade, the column length was reset back to 32 and data in those column was truncated.

Any solution to store 50 characters in those columns?
Thanks