Hi,
Try changing the Title Format and Image Format unit options.
Title Format:
<h5 class="amazon-product-title">
<a href="%href%" title="%title_text%: %description_text%" rel="nofollow noopener" target="_blank" onclick="window.open('%href%','popup','width=600,height=600')">%title_text%</a>
</h5>
Image Format:
<div class="amazon-product-thumbnail" style="max-width:%image_size%px; max-height:%image_size%px; width:%image_size%px;"">
<a href="%href%" title="%title_text%: %description_text%" rel="nofollow noopener" target="_blank" onclick="window.open('%href%','popup','width=600,height=600')">
<img src="%src%" alt="%description_text%" style="max-height:%image_size%px;" />
</a>
</div>
What this doing is basically inserting onclick="window.open('%href%','popup','width=600,height=600')">
in the a tag. Change the part, width=600,height=600
to set your desired pop-up window size.
If the change does not reflect, you need to add onclick
via Dashboard -> Amazon Auto Links -> Settings -> Misc -> Form -> Allowed HTML Tags.
Hope this helps.