If the 1099-B (or equivalent form) does not report your cost basis and/or holding period, you have to provide the "Cost or other basis" (Box 1e) from your records and the " Date acquired" (translates to holding period, short-term or long-term). If you do not have good records of this information, your only option is to make a good-faith effort to estimate the cost-basis and date of acquisition. Any 'reasonable' approach should suffice.
If don't know the date, but know that you had held it for more than a year (long-term),
you can enter a date that is
more than one year before the sale date.
If don't know the date, but know that you had held it for a year or less (short-term), you can enter 01/01/2017 as the date acquired.
"Gold" (physical gold or shares backed by physical gold) are taxed as Collectibles, so be sure to make that selection when asked to identify the Type of Investment (see sample screenshots for 1099-B and No 1099-B).