Hello Susy,
Arimidex is hormone therapy, not chemotherapy and you'll find lots of information about this and Tamoxifen on the hormone therapy board. Which drug you take after the menopause will depend very much on your circumstances and your onc: you may just stay on Tamox for 5 years as you can take this pre- and post-menopause, or your onc may decide to switch you to an Aromatase Inhibitor, such as Arimidex, IF you go through the menopause. Your onc is really the only one who can tell you what the plan is.
Good luck with your treatment, Angelfalls