There is no upgrade path from older Filemaker versions, you purchase Filemaker ver 13. https://store.filemaker.com/US/ENG/RTL/product/purchase/
If you have individual licenses of FileMaker Pro 13, 12, 11, or 10, or FileMaker Pro 12, 11, or 10 Advanced, you are eligible for upgrade pricing on FileMaker Pro 13 Advanced. Upgrade eligibility for version 10 ends September 27, 2014.
FileMaker Pro can directly open or convert your existing FileMaker Pro 12 (.fmp12) and FileMaker Pro (.fp7) 11, 10, 9, 8 and 7 databases. All other versions of FileMaker Pro will require a multiple product conversion. Review the information below to determine whether your files will directly convert to FileMaker Pro, or if they will need to be converted multiple times.