You may have your reasons for buying that 32-bit, unsupported version of Ubuntu. If it was just a misunderstanding then I suggest you get this: https://www.amazon.com/Ubuntu-Linux-18-04-DVD-OFFICIAL/dp/B07CWLKBDY/ref=pd_aw_sim_sbs_147_1?_encoding=UTF8&psc=1&refRID=SR70KC2BZ2E4R4ETF3X1

Also, any OS is only as secure as YOU make it.