Yes, you can use this app in Classic too. To access the Quick Update Translations app in classic, follow the below steps:
- Click on the App Menu drop-down (present at the top right side of the page).
- Select Quick Update Translations App.
P.S. Discover Quick Update Translations, the simple way to update Labels and Translations in just a few clicks. Find it on AppExchange: https://appexchange.salesforce.com/appxListingDetail?listingId=fa9afbfe-74ff-4027-ac32-2cdfd58184d3