how to calculate tonnage of steel

{"cid":"91184445","title":"Steel Tower, Tubular Tower, Light Pole Hot Dip Galvanizing Zinc Tank","imgUrl":"https:\/\/img.chinax.com\/nimg\/8f\/66\/666e0e5471bb687cf0f820dfc8db-200x200-1.jpg","attrs":{"Price":"USD","Brand Name":"XIN LINGYU","Model Number":"According according requirement","Minimum Order Quantity":"1","Delivery Time":"90 DAYS","Place of Origin":"CHINA","Payment Terms":"L\/C, T\/T, D\/P, D\/A","Supply Ability":"10 PIECE \/YEAR","Packaging Details":"CONTAINER","Brand Name:":"XIN LINGYU","Place of Origin:":"jiangsu, China (Mainland)","Certification:":"ISO9001","After-sales Service Provided:":"Overseas third-party support available","Material:":"SMC,FRP,GRP","Technique:":"Sheet molding compound"}}

{"cid":"91149008","title":"Frac Sand Tanks: Where Abrasion, Not Corrosion, Sets the Design","imgUrl":"https:\/\/img.chinax.com\/nimg\/14\/cb\/b5d606076069c13b1061ae2ea50e-200x200-1.jpg","attrs":{"Price":"$5000~$20000 one set","Brand Name":"CEC TANKS","Model Number":"W","Minimum Order Quantity":"1set","Delivery Time":"10-30 days after deposit received","Easy to clean":"Smooth, glossy, inert, anti-adhesion","Payment Terms":"L\/C,T\/T","Corrosion Integrity":"Excellent","Size Of Panel":"2.4M * 1.2M","Steel plates thickness":"3mm to 12mm , depends on the tank structure","Certification":"ISO 9001:2008, AWWA D103 , OSHA , BSCI","Chemical Resistance":"Excellent","Place of Origin":"China","Supply Ability":"60 sets per month","Tank body color":"Dark green \/ can be customized","Packaging Details":"PE poly-foam between each two steel plates ; wooden pallet and wooden"}}