Coverting old PowerPoints into new formatting

Hello Alexandra,

Thank you for your question. When converting PowerPoint slides, the best practice would be to export slides to a second deck (template) which is set up with your desired themes.

In the template (second) deck, head over to Design, then click the More button (the drop-down button to the right of Variants).

Here, you can set up colours, fonts, effects and background effects.

Now, when you copy slides over from the original (old) deck, you can ask PowerPoint to match destination themes.

Fonts, colours and slide backgrounds will be updated to reflect the new deck's themes.

I hope this helps. If you need further assistance, please do ask again.

Kind regards
Marius Barnard
STL