Finding the QuotesDLX Block
This will help you with finding the block in the WordPress block editor.
Within the Block Editor, click the "+" icon to add a block.

The "+" icon is the block inserter
In the search, type in
quotesdlx
and from there you will be able to insert the block.
The QuotesDLX Block in the Block Inserter
The block itself is under the
Text
category.
QuotesDLX Block Category