To transform PowerPoint slides into a new template, follow these steps:

Step 1: Choose or Create a New PowerPoint Template
Open PowerPoint and go to File > New.
Choose a built-in template or download one from Microsoft Templates or a third-party site like Envato Elements or Canva.
If you have a custom template, open it and save it as a .POTX file.
Step 2: Apply the New Template to Existing Slides
Option 1: Use the Slide Master
Open your existing PowerPoint file.
Go to View > Slide Master.
Click Themes and select the new template.
Adjust fonts, colors, and layouts to match the new design.
Option 2: Copy Slides to the New Template
Open the new template in PowerPoint.
Go to Insert > New Slide > Reuse Slides.
Click Browse and select your old PowerPoint file.
Right-click on a slide and select Insert Slide (choose Use Destination Theme to match the new design).
Step 3: Adjust Formatting & Layouts
Review slides for misaligned text, images, or colors.
Use Design > Slide Size to ensure proper formatting.
Apply consistent fonts and styles using the Design tab.
Update charts, tables, and SmartArt to match the new template's style.
Step 4: Save & Export the Final Version
Save the new presentation as a PPTX file.
Export as PDF or video if needed (File > Export).
Review all slides for consistency and readability.