One redirect from http:example.com/abc to https://www.example.com/abc

Website, Application, Performance Security
1

I have heard that one redirect will lose 1% to10% link juice. I would like use redirects as less as possible.
I see some website use one redirect to redirect from http://www.example.com to https://example.com.
What is the best way for me to use one direct to always redirect to https://www.example.com?

2

Pretty easy. you just need a page rule such as:

If the URL matches: example.com/*
Then settings are: Forwarding URL, https://www.example.com/$1

If you also want to catch non-SSL traffic hitting the www subdomain then you can also additionally define the page rule:

If the URL matches: http://www.example.com/*
Then settings are: Forwarding URL,https://www.example.com/$1

As only one or the other will ever be triggered you are not introducing any extra redirects having both in place.