Explanation:

- The passage narrates the experience of a person who ventured out on a voyage, gained wealth, and is now ready for another adventure.

- Blank (5) follows a comma and precedes the description of finding a new ship.

Options explained:

1. Option 1: where - This indicates a location which fits well here since it talks about the location where he found the new ship.

2. Option 2: wherever - This implies any place and doesn't suit the context of a specific location.

3. Option 3: while - This suggests a time-related context, not fitting here describing a place.

4. Option 4: when - This indicates a time, which doesn't fit the need for a locational reference.

- Therefore, the correct answer is "where," as it appropriately indicates that Basra is the specific place where the protagonist found the ship.