** Supermarket chain owner's shares up 17.8 pct at $38.50 premarket
** Says exploring conversion of about 200-300 stores to a real estate investment trust (REIT) and offer it to shareholders through rights offering to raise cash
** Says raised about $300 million from selling part of stake in Sears Canada through a rights offering as of Nov. 6.
** Company has closed stores, slashed inventory and sold off assets to generate cash after a decade of falling sales
** Up to Thursday's close, Sears Holdings stock had fallen about 12 pct this year