How do I understand 能 in 请问几天能到?
A: &quot;小姐， 我想寄一个包裹。&quot; (Miss, I want to mail a parcel)
B: &quot;请问寄到哪儿? 寄什么?&quot; (May I ask, where are you mailing it to? And what you are mailing?)
.......
A: &quot;请问几天能到?&quot; (may I ask, in how many days can it arrive?)

能 = can ; 到 = arrive

几天能到? =  can arrive in how many days?

会 = would/will

几天会到? = would/will arrive in how many days?