Upgrade fail from 1.5.6 -> 3.0.2.0

I have not been able to update my cart in a while. This is getting so irritating that it is not funny. This is my second attempt and now I have to restore my entire web file set- yet again!

The install page I went to says anything before 1.5.4 is not supported but I have 1.5.6 so I "assume" this upgrade is supported YET when I try I get this error message:

SyntaxError: Unexpected token < in JSON at position 0 OK Unknown: mysql_connect(): The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead in /home4/thejoys3/public_html/www.mycart.com/system/library/db/mysql.php on line 7{"success":"Patch 1000 has been applied (1 of 10)","next":"index.php?route=upgrade\/upgrade\/next&step=2"}

Can someone PLEASE help me out here.... I have tried renaming the commands, the mysql.php and mysqli.php files and other things but I still cant get this darned upgrade to work.

I need "detailed" help instructions... please help.

Well, just search Google on this, and you will find bulkloads of infos on this:
mysql extension is deprecated
https://www.google.com/search?q="mysql+ ... "+Opencart
---
But better also check the forum about
upgrade OC 1.5.6
search.php?keywords=upgrade+Opencart+1.5&terms=all
---
to then find out, that you cannot UPGRADE OC, only install later Version Software, in full.
And forget everything about Theme and/or Extensions, used in the old Version, because
not one of them will further function. It's all written and explained, multiple times, and in
details, so, you cannot miss it, if you care to search for, here and in Google as well.
Ernie