How long do I need to stand in line to get a good spot in the pit?

So, in a couple weeks I'm going to see Sabrina Carpenter in Milan. It's my first time in the pit, and I don't want to end up stuck at the back of the arena considering it's freakin gigantic, and yes I'm a tall girl but still, can't be too fun. There's no way I'll be at the VERY front considering there's a higher "quality" package above mine for that spot, I got the cheaper one which means I'm in the area behind that, but considering she's a big popstar and there's gonna be tonnes of people, how long before the actual opening time should I start queuing? I feel like if I get there even less than 3 hours before I'll be stuck in an awkward spot? Idk, frequent large concert goers help!!