How should cashing crypto altcoin to USD be listed on Schedule D/Form 8949?

Hi /r/tax, I was wondering if any of you could clarify this for me.

For example, I made a net gain of $1000 from an altcoin on another exchange. I convert that altcoin to Bitcoin and send that Bitcoin to another exchange so I can cash out to USD.

Listed as the following:

1. Net gain of $1000 in altcoin, converted to Bitcoin
2. That Bitcoin is sent from one exchange to another
3. That Bitcoin is immediately cashed out for USD.

Both 1 and 3 are taxable events, so how should this be listed on Schedule D/Form 8949? Should the $1000 gain from altcoin to USD be listed as one transaction or does the $1000 gain from converting altcoin to Bitcoin and Bitcoin to USD be considered separate, resulting in the $1000 gain being taxed twice?

Thank you for any clarification.