If this is on a computer dedicated to this one database (at that size, I'm going to guess yes?), then you can probably check the disk I/O usage, I'd expect to see disk activity, and I'd let it run 6+ hours then check the console for updates. It looks like it has been 24 hours since you posted, do you have a percentage output now?
Regarding restore time, that depends on a number of factors (e.g. disk speed, CPU load), and 1.5TB is a bigger neo4j db than I've run so far.
As an example, as luck would have it I'm currently restoring a 1TB+ postgres database and it's been running since yesterday. I know it is still running because I can see a lot of activity on those disks, and about every 3-4 hours pg_restore says "creating...." something different.
I know this is a different database type, but it is an example that is smaller than yours and taking more than 24hours+, and I'm only restoring (you are also migrating the db)